Ruined world

A long time ago, further than any written history, a great civilization thrived. The only reasons anyone knows of its existence is the alien creature the elder gheforis has as a host and the countless masses of ruined cities of crystal, stone, and crumbling flame scattered all across the globe. Most are modest, the size of cities build in modern times, but the testament to the generations accomplishment is the sea of buildings in Sonata.
Sornata would have been part of Whidyr or Hasehak, if the city had not been so evident. The single city with lake-wide roads and sky-piercing buildings spanned so far and so wide that an entire continent was covered. Sornata is only an ezivald or continent due to it being the city itself. The city has long been abandoned by its prior host, and has been repurposed by many creatures as home. But the city is so vast and so tall that there are still nooks and crannies that have remained unexplored.
Even beyond Sornata, architecture of the previous era is dotted all over. Underground, underwater, in the sky, everywhere there are remnants of the once great civilization. Many smaller ruins have been destroyed and looted, but the sheer number of structures leaves plenty more to be discovered.